The need for effective and economical preservative compositions is well known. There are a wide variety of applications where inhibiting the growth of microorganisms is necessary, as for example personal care products such as shampoos, creams, lotions, cosmetics, soap and household products such as laundry detergents, hard surface cleaners, and fabric softeners. The shelf life of these preparations depends on their resistance to microbial spoilage.
In addition, in many industrial applications, antimicrobial agents are useful in paint, wood, textiles, adhesives, sealants, leather, rope, paper pulp, plastics, fuel, oil, and rubber and metal working fluids. The control of slime-producing bacteria and fungi in pulp and paper mills and cooling towers is a matter of substantial commercial importance.
For the foregoing applications the demand for stable broad-spectrum preservatives has increased. In recent years, these needs have been met with solid formulations. For example, combinations of formaldehyde donors (e.g., dimethyloldimethylhydantoin (DMDMH)) and halopropynyl compounds (e.g., 3-iodo-2-propynylbutyl carbamate (IPBC)) have achieved considerable commercial success. Such synergistic combinations have been described in U.S. Pat. No. 4,844,891.
Furthermore, because of the demand of governmental regulations, low free-formaldehyde products are needed. Research in this area has also proved beneficial. For example, in the case of DMDMH, improved formulation and processing has resulted in compositions which contain less than 0.1% free formaldehyde. (See U.S. Pat. No. 5,405,862.) In contrast, earlier formulations of DMDMH had over 1% of free formaldehyde. (See U.S. Pat. No. 3,987,184.)
At the present time, in addition to meeting the above criteria, the industry is demanding liquid forms of preservatives as the use of automatic liquid blending systems becomes more popular. Unfortunately, preservatives that are in liquid form, highly stable, broad spectrum, and low in free formaldehyde have eluded formulators.